Field
Various communication systems may benefit from indications of conditions existing within the system. For example, communication systems employing dual connectivity may benefit from an indication of whether or not a user equipment is in a dual connectivity synchronized condition.
Description of the Related Art
Dual connectivity (DC) in the third generation partnership project (3GPP) may be regarded either as synchronized DC or unsynchronized DC. Sometimes unsynchronized DC can be referred to as asynchronous DC or asynchronized DC. DC implementation can depend on the deployment scenario and network. For example, it may be that as long as the timing difference between the primary cell (PCell) and the primary secondary cell (PSCell) is below 33 μsec, the DC scenario can be regarded as synchronized—otherwise the DC scenario can be regarded as not synchronized (async).
In the context of dual connectivity the cells, such as PCell and PSCell, may be assumed to be on different frequencies and belong to different evolved Node Bs (eNBs). Such a deployment may limit the use of certain network (NW) synchronization techniques and may more easily lead to situation where timing drift between the cells may occur more often.
Furthermore, there may be two categories of user equipment (UE). The first category can be UEs that support synchronized DC. The second category of UEs can be UEs that support both synchronized and asynchronized DC. An indication of which category applies to a given UE can be provided by the UE. This indication may be signaled to the network, for example in the form of a UE capability.
For Rel-12, the supported scenarios may only have one cell per cell group (CG). Thus, there may be a PCell and a PSCell only without further SCells in either CG. Additional cases may be supported in later releases. When discussing whether the DC is in a sync or async DC scenario the issue can relate to the observed timing difference between the PCell and PSCell, disregarding whether SCells are configured or not. The SCells may anyway be synchronized to the PCell or PSCell according to whether they are configured by the PCell or PSCell.